This invention relates to an improved liquid alkenyl succinic anhydride mixture having superior paper sizing properties. This invention also relates to an improved method for the sizing of paper and paperboard products. A further aspect of this invention relates to an improved method for imparting water-repellency to cellulosic fabrics.
It is known in the art that long straight chain alkenyl succinic anhydrides can be used as effective paper sizing agents. See, for example, U.S. Pat. Nos. 3,102,064; 3,821,069; 3,968,005; and 4,040,900 (Re. 29,960). These alkenyl succinic anhydrides have also been used as fabric treating agents. See U.S. Pat. No. 2,903,382. The useful molecular weight range of the alkenyl group on these sizing agents has variously been described as encompassing 8 to 35 carbon atoms.
It is also known that these prior art sizing agents are best applied in a highly dispersed form, such as an aqueous emulsion. However, alkenyl succinic anhydrides made from straight chain alpha olefins are solids at ambient temperatures and are therefore not effective in forming these emulsions. In view of this, commercial alkenyl succinic anhydride paper sizing agents are made from isomerized straight chain alpha olefins (i.e., straight chain internal olefins) or from branched chain olefins. See, for example, the frequent reference to "isooctadecenyl succinic anhydride" in U.S. Pat. No. 3,102,064.
It has been taught that the molecular weight of the alkenyl group of the more effective or preferred alkenyl succinic anhydride sizing agents corresponds to a carbon number in the 13 to 22 carbon atom range. Mixtures of several carbon numbers have also been described. See, for example, the reference to C.sub.15-20 alkenyl succinic anhydride in U.S. Pat. No. 4,040,900 (Re. 29,960).